Development status of EUVL mask blank and substrate

Asahi Glass Company (AGC) has been developing the extreme ultra violet (EUV) lithography mask blank and polished substrate since 2003, including the developments of all essential materials and processes: the low thermal expansion material (LTEM), the material developments of the reflective, capping and absorber films, the process developments of the substrate polishing, cleaning, film deposition and resist film coating processes. In this paper, we present the current development status of the full-stack EUV mask blank and polished substrate which are the most suitable for the EUV lithography process development with EUV pre-production exposure tools. We report the development progress of the reflective multilayer-coated LTEM substrate by showing its critical performances with those of 2010 achievements, which include the substrate flatness, the EUV optical properties of the Mo/Si reflective layers and the defect of LTEM substrate and reflective layer. The performances of the Ta-based absorber and the resist films are explained as well to show the readiness of the EUV mask blank suitable for various kinds of process developments of the EUV lithography.